Fixing drafty horizontal crack in foundation

I have a small cold room (~7'x7') in my basement in a corner of the foundation. The area surrounding this room is finished / insulated. There is a horizontal crack close to the top edge of one of the foundation walls in this cold room, below the rim joists (circled in the picture).

I've been told by some contractors that this happens when the foundation was originally poured too short and they topped it off afterwards, which usually results in the top layer not fully adhering to existing foundation (though no way for me to verify that).

My issue is that there is a strong draft coming through parts of this crack and it looks like some of the stuff above the crack is a bit loose and ready to fall off (I think this is a thin/superficial layer flaking off, but can't tell for sure before taking some of it off - might even be just the white coating which I'm not familiar with, (fire- or waterproofing?). The crack is definitely drafty though.

I'm looking for some guidance and advice on how to fix this drafty foundation wall as it makes the finished space rather uncomfortable. I'm not looking to fully condition this room, but currently it gets way too cold in there and the biggest contributor seems to be the draft from the crack.

Any ideas on how to approach this would be much appreciated!


Drafty foundation wall crack

 

You might want to lightly chip away a little bit off of the thin side of the crack so that you create a "V" notch. (Use a hammer and cold chisel). Then you could either use an anchor epoxy (comes in a caulking tube with a long mixing nozzle) or a concrete sealant / caulk such as Loctite S10. Inject it into the crack with your caulking gun. Tool any excess caulk out flat with a paint stick or disposable putty knife. If the crack is also on the outside you will do it there too.

 

You actually feel air coming through the cracks themselves? That means the cracks go all the way through the wall and are open to the outside air. That does not seem right. I can picture the draft coming from the sill plate that may not be level with the top of the concrete. What does the other side of the wall look like?

 

Thanks for the quick replies!

There is definitely a draft coming from some parts (the middle) of the crack, but not all the way along it. It is possible that air is leaking through the sill plate and getting under the loose (and hopefully superficial) layer between the sill plate and the crack and coming out of the crack. I don't think I could tell for sure without removing some of it, though?

The other side of this crack is a few feet below grade so I'd have to dig outside to see how it looks (not possible right now due to frozen ground). I should also say that there has never been any water leaks through this crack if that makes a difference, and the soil on the other side gets soaked at least a few times a year in heavy rain.

Do you recommend removing some of the layer between the crack and the sill plate to see what it looks like underneath?

 

No! I say do what Xsleeper has recommended and see what happens. I would also add more insulation at the top and cover the edge as well.

 

Ok, I'll give that a shot, thanks so much to you both!

Do you mind elaborating on "I would also add more insulation at the top and cover the edge as well." a bit?
Do you mean replace the fiber glass with something else and make sure it covers the seam between the sill plate and foundation wall? If yes, I'm not sure what to use here or how to seal it...

 

Just use some more fiberglass and let it drape over the edge. You might use some aluminum tape to fasten it to the wall to make seal of sorts.

 

Ok, will do, thanks!

Would you recommend insulating the interior walls in the cold room as well?

Currently there is only drywall on the warm side of the walls and exposed framing on the cold side.

I've been thinking of using batts and a vapor barrier as shown below, but I'm not sure if that's a good idea or asking for trouble (and I'm not sure if I can fully seal the door beyond adding some weatherstripping).

 

Sure, if you want to maintain the heat in that room (I'm assuming you have a space heater or something in that room) and not dissipate to the other areas. No harm done. But you might want to put insulation on the exterior walls also.

 

My motivation for wanting to add VB/batts (red/blue in the pic) on those 2 interior walls was to keep the cold room cool and the finished/conditioned space more comfortable... not planning to heat the cold room, if that's what you meant.

 

Well, unless there is an added source of heat or cooling, the temperature will equalize throughout the area. That is why I never understood why contractors put in a heating duct on an interior bathroom. Being below grade (usually with insulation attached to the area that might be above grade), basements normally will be the same temp through the area. So yes, the bear concrete wall will add some cooling, but it's negligible.

edit...I missed the part about the rest of the area being conditioned. So yes the insulation will keep the room cooler.

 

I'm having a hard time believing that a crack on the floor has any kind of draft coming through it. As Norm stated that would mean you have a path from the floor all the way up to the exterior of the foundation, a much greater problem than just a crack needing filling!

​​​​​​​Are you sure about that?

 

Marq, that's not the floor. Take another look at the picture. That's the basement ceiling.

 

​​​​​​​